1. Field of the Invention
This invention relates to the conveying of material and objects by endless belts and especially to belts directed around curves in the vertical or horizontal directions. The invention also relates to long conveyors and especially to conveyors for transferring material where the height of the conveyor is limited as by the thickness of a vein of coal being mined.
2. Description of the Prior Art
The applicant has previously designed a belt and conveyor system in an attempt to convey material around curves and the belt conveyor is described in U.S. Pat. No. 3,701,411 whereas the belt construction is described in U.S. Pat. No. 3,545,598.
U.S. Pat. No. 3,545,598 describes a belt having a central longitudinally extending inextensible spine and corrugations extending from the spine transversely to the edges supported on moving surfaces extending at an angle to the corrugations for bridging the grooves of the corrugations.
U.S. Pat. No. 3,701,411 describes a conveyor system in which the belt of U.S. Pat. No. 3,545,598 is supported on a mobile conveyor system having a self-propelled tractor pivotally connected at each end of a chain of pivotally interconnected, single axle carriages.
Two-belt conveyor systems where one belt drives the other belt have been devised in the past and the following patents are representative of some of these systems:
U.S. Pat. No. 3,261,452 describes a belt conveyor system in which there are two belts. One of the belts drives the other belt and both belts have separate tensioning means or take-ups.
U.S. Pat. No. 3,268,065 describes a two-belt system in which the drive belt has a ribbed surface for engagement with the ribbed surface of the load-carrying belt to provide better frictional contact between the belts. The patent also describes apparatus for aligning the drive belt with the conveyor belt so that the ribbed surfaces match. The load-carrying belt is shaped by troughing rollers at the sides. Separate take-ups are provided for the two belts.
U.S. Pat. No. 3,557,941 describes a two-belt system in which the load-carrying belt has hinged sides and laterally extending reinforcing members made up of three metal strips disposed in end-to-end relationship. A layer of fabric is embedded in the belt and extends longitudinally thereof. The hinged sides of the load-carrying belts are supported in a troughed position by outwarding protruding projections or support shoes which engage grooves in the drive belt.
While these patents and other described two-belt systems, they do not show systems in which both belts are tensioned by the same take-up. Also, the belts must be trained by a roller adjustment and relative lateral movement of the drive belt with respect to the conveyor belt is prevented. In none of these patents are both belts passed around the same terminal pulley nor is the container belt made with transversely extending reinforcing members and elastic material between the transverse members for stretching of the container belt in the longitudinal direction so that both belts can be passed over a single terminal pulley without relative slippage between the two belts.
U.S. Pat. No. 3,144,929 describes a single belt conveyor for transporting fluent materials such as particulate solids, slurries and liquids. The belt has a U-shaped cross section which is filled by a second belt means or insert for uphill or downhill runs. Elongation of the belt is not to exceed one or two percent. The belt is relatively thick in relationship to its overall width to maintain its shape and provide rigidity in operation. While this patent shows a belt with a U-shaped cross section, it does not describe a two-belt system in which the container belt in thin-walled and reinforced by transverse U-shaped reinforcing members with elastic material between the members to permit stretching of the container belts in the amount of up to 25 percent elongation as in the present invention. The patent also does not describe a conveyor capable of conveying bulk materials such as large rocks and coal where heavy loads must be carried and wear and maintenance are important considerations as in the present invention.
Belts have also been devised with elastomeric material and transverse reinforcement to provide transverse stiffness. For example, U.S. Pat. Re. No. 26,731 describes a flat belt having two parallel layers of flexible metal cords which extend transversely across the belt in combination with one layer of woven fabric or longitudinal textile cords extending between the metal cord layers. The woven fabric or textile cords limit belt stretch and provide a main tension layer.
Great Britain Pat. No. 1,083,536 dated Sept. 13, 1967 describes a flat belt conveyor system having only one belt and transversely extending steel rods to provide transverse rigidity. The transversely extending reinforcing rods do not extend into the side ribs and there is no drive belt so that the belt construction must include longitudinal reinforcing members to carry a load such as that indicated by the deflection of the belt. This reinforcement may be the canvas or other textile material wrapped around the rods.
In neither of these patents is there shown a belt in which there are transversely extending reinforcing members with elastic material between the reinforcing members being stretchable in a longitudinal direction as in the container belt of the present invention. Also, there is no showing of the reinforcing members extending into upwardly extending side members of the container belt to maintain a U-shaped cross section of the container belt as in the present invention.